A placebo-controlled, double-blind, 2 x 2 factorial design, parallel-group, randomized clinical trial examining if chronic treatment of Huntington Disease (HD) with CoEnzyme Q10 and remacemide, alone or in combination, will slow down the progressive functional decline experienced by HD patients. Three hundred and forty stage I or II HD patients will be randomized to one of four treatment groups: CoEnzme Q10, remacemide, CoEnzyme Q10 and remacemide, double placebo. The subjects will be followed for 31 months for adverse events and for changes in vital signs, electrocardiogram, and surveillance laboratory tests. Neuropsychological and neurological tests will also be regularly performed as well as blood levels of CoEnzyme Q10 and remacemide. A subset of subjects will have brain lactate levels measured by magnetic resonance spectroscopy. The primary outcome variable is the change in total functional capacity from baseline to 30 months, and the analysis, assuming a 15% dropout rate, will have greater than 80% power to detect a 40% slowing of total functional capacity decline. An analysis of covariance with CoEnzyme Q10 treatment and remacemide treatment as factors of interest, investigator as the stratification factor and baseline total functional capacity as a covariant will be done. F-tests will be performed for significance of the main effects of CoEnzyme Q10 and remacemide and confidence intervals will be constructed for each of these effects. A two-sided significance of 0.05 will be used for each of these tests, and confidence coefficient of 0.95 will be used for interval estimation.